Leader’s right hand fails to regain leadership of conservatives in parliament

BERLIN—Angela Merkel’s grip on power took a severe blow on Tuesday when her party’s lawmakers ousted a close ally of the German chancellor as their parliamentary leader and replaced him with a candidate she had refused to endorse.

The affront—Ms. Merkel’s protégé had been the conservatives’ parliamentary floor leader for all 13 years of her successive terms—is the latest and most telling sign of the erosion in the chancellor’s authority since she delivered her party’s worst performance in seven decades at last year’s general...